2012 was so darned hot — globally and in America

The average global temperature for 2012 was the ninth warmest the world has recorded in record-keeping that dates to 1880, while the continental United States experienced its hottest year in history, according to the National Aeronautics and Space Administration.

“With the exception of 1998, the nine warmest years in the 132-year record all have occurred since 2000, with 2010 and 2005 ranking as the hottest years on record,” reported NASA’s Goddard Institute for Space Studies, which monitors the world’s climate.

The average global temperature in 2012 was about 58.3 degrees Fahrenheit, which is 1 degree Fahrenheit warmer than the mid-20th century baseline.

“One more year of numbers isn’t in itself significant: What matters is this decade is warmer than the last decade, and that decade was warmer than the decade before: The planet is warming. The reason it is warming is because we are pumping increasing amounts of carbon dioxide into the atmosphere,” said NASA’s report.

Carbon dioxide is the greenhouse gas that traps heat and largely controls the Earth’s climate.

The carbon dioxide level in the atmosphere in 1880 was about 285 parts per million. By 1960, carbon dioxide measured at the observatory atop 13,677-foot Mauna Loa on Hawaii was 315 parts. Today, the level exceeds 390 parts per million — and has exceeded 400 parts at some monitoring stations in the Arctic.

The Arctic is experiencing the world’s most rapid global warming, and saw the extent of its summer icepack shrink to a record low in September 2012.

The world experienced weather extremes in 2012, notably a drought that at one time attained moderate to severe levels over 61 percent of the lower 48 states. And more than 100 million Americans experienced at least 10 days of above-100-degree heat.

“The U.S. temperatures of the summer of 2012 are an example of a new trend of outlying seasonal extremes that are warmer than the hottest seasonal temperatures of the mid-20th Century: The climate dice are now loaded,” said Dr. James Hansen, director of the Goddard Institute for Space Studies.

“Some seasons will be cooler than the long-term average, but the perceptive person should notice that the frequency of unusually warm extremes is increasing.”

Impacts of climate change are notable in the Northwest, from rapid shrinking of the South Cascade Glacier — monitored since 1950 by the U.S. Geological Survey — to increasing acidification of the region’s coastal waters. The Washington shellfish industry has been forced to move hatcheries to Hawaiian waters.

Earlier this week, Seattle heard a prediction that rising sea waters will encroach on its working waterfront by the end of the 21st century.

A second government study out this week, by the National Oceanic and Atmospheric Administration, pegged 2012 as the 10th hottest year on record.

“Both reports were independently produced: It’s actually a good thing both reports have slightly different results as it allows for a more accurate overall picture of the climate,” John Wald of NOAA told the Talking Points Memo web site.